The use of chemicals in cleaning, and particularly cleaning with chemicals diluted in water to form aqueous cleaning solutions, is used in a variety of fields and in a variety of applications. In particular, a market has emerged over the last several decades for automated car washes, and particularly drive-through car washes, as more and more people no longer have access to self-wash facilities or the time to clean their own cars. As drive-through car washes often involve applying large quantities of several different cleaning solutions to each vehicle, the increased popularity of drive-through car washes has generally led to widespread use of cleaning and treatment chemicals in large quantities. Furthermore, competitive pressures to adequately clean cars for repeat business encourage excessive chemical usage beyond the necessary amount to ensure each car is fully cleaned. The widespread and often excessive use of the typically hazardous cleaning chemical can result in discharge of the chemicals into lakes, streams and waters contaminating the environment and ground water. In response to the increased and widespread use of cleaning chemicals in car washes, government regulations controlling the use of the cleaning chemicals have become farther reaching and stringent to encourage careful management of the chemical usage.
A typical car wash with chemical dispensing system operates by diluting a quantity of a concentrated cleaning chemical with washing water. Typically, a bulk container containing the concentrated cleaning chemical is connected to a venturi style eductor linked to a process water supply. The bulk container can contain a float to sense the tank level or can be manually refilled when the concentrated chemical is exhausted. The eductor crudely dilutes the concentrated cleaning chemical with the process water as the water flows through the eductor to form an aqueous cleaning solution, which is often stored in a batch tank before being applied to a car. An injector pump can then be used to pneumatically dispense the aqueous chemical solution onto a car. While the dilution system is a relatively simple concept, maintaining and fine tuning the dilution rate of the cleaning chemical is difficult as a number of constantly changing process variables can cause the dilution rate to change. The process variables can include, but are not limited to, the relative concentration of the batching process, the dosing pump rate, and the pressure and flow rate of the incoming process water.
As a result, the typical car wash cannot accurately track the real time chemical usage or can only roughly estimate the actual chemical usage per washing event. Typically, operators can only estimate the usage of the cleaning chemicals per washing event by dividing the bulk amount of cleaning fluid used by the car wash for a given period by the estimated amount of cars washed during that period. Consequently, accurate real time analysis of the chemical usage is often difficult if not impossible.
Furthermore, many car wash systems rely on relatively inaccurate high volume dosing pumps and eductors, which can handle large quantities of cleaning solution, but can cause the dilution rate to vary significantly. As a result, dilution ratios produced by even the best systems can vary substantially with each wash and can change without notice from batch to batch and even the dilution within a single batch. Consequently, even if real time measurement and tracking of chemical usage was practical, the dosing systems themselves require constantly monitoring and adjustment, which is often cost prohibitive given the manual monitoring and adjustment required.
Similarly, the cleaning chemicals themselves can prevent the use of many types of more sophisticated fluid monitoring devices. The cleaning chemicals used for cleaning cars are typically very corrosive and/or oxidizing. Sensitive fluid monitoring devices can be damaged by the cleaning chemicals themselves, preventing accurate measurement of the chemical fluids.
While systems for monitoring and controlling the dispensing of chemicals are available, the presently available systems are typically “open-loop” processes. Open-loop control processes monitor the input into a system to determine if corrections to the system are required based on the conditions of the input stream. However, open-loop processes do not monitor the output from the system for feedback on the effectiveness of the changes to the system, which can cause the open-loop process to miss errors in the system. Despite the potential inaccuracy with open-loop processes, open-loop processes are typically used in car wash systems as significantly cheaper than alternative processes.
Improved venturi eductors, such as the CHEM-FLEX injector manufactured by Hydra-Flex Incorporated of Burnsville, Minn., provide more stable dilution rates by eliminating the need for an intermediate batching process and the associated process variables. The reference is herein incorporated by reference in its entirety. However, CHEM-FLEX injectors are still ultimately limited by the properties of chemical input into the injector, of which there is no convenient method of monitoring and adjusting. As a result, even the improved CHEM-FLEX injectors cannot provide sufficiently constant dilution rates.